Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

187
CHAPTER 7
NUTRIENT STRESS
K. JANARDHAN REDDY
Department of Botany, Osmania University, Hyderabad 500 007, India
(e-mail: kjreddy50@yahoo.co.in)
Key words: Calmodulin, deficiency symptoms, essential elements, glutathione,
growth, phytotoxicity
1. INTRODUCTION
Mineral nutrients are essential for normal growth and development of plants. The
phenomenal growth of knowledge made in the areas of the mechanism of the ion uptake,
the critical role of minerals in the basic processes at cellular level and molecular
approaches to the study of mineral nutrition have raised the status of mineral nutrition
of plants as an independent discipline of the plant biology (Epstein, 1972; Mengel and
Kirkby, 1978; Clarkson and Hanson, 1980; Marschner, 1995; Loneragan, 1997; Grossman
and Takahashi, 2001).
Chemical analysis of plants revealed the occurrence of about 60 elements in
different tissues although only 17 elements are essential for growth and metabolism.
These seventeen elements were classified into two groups depending on the
concentration needed by the plants and they were designated as macro and micro
nutrients. Ideally the classification should be based on biological structure and metabolic
function. According to Mengel and Kirkby (1978) they were divided in to four groups
depending on their chemical nature. The first group includes C, H, O, N and S, which in
reduced form are covalently bonded constituents of the plant organic matter. The second
group consists of P and B which occur as oxyanions, phosphate, borate and silicate.
The third includes K, Na, Ca, Mg, Mn and Cl, which are associated with osmotic and ion
balance roles. The fourth group of plant nutrients is made of Fe, Zn, Cu and Mo. These
elements are present as structural chelates or metalloproteins.
The nutrient requirement of plants can be assessed roughly by inorganic
composition of the plant. Plant dry matter constitutes 10-20 percent of the fresh weight.
Nearly 10 percent of the dry matter consists of mineral elements. The mineral composition
of plants show a lot of variation and is influenced by several factors such as genetic
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K.V. Madhava Rao, A.S. Raghavendra and K. Janardhan Reddy (eds.),
Physiology and Molecular Biology of Stress Tolerance in Plants, 187–217.
© 2006 Springer. Printed in the Netherlands.